1. Field of the Invention
The present invention relates to a motor actuator used for a power window device that opens and closes a vehicle door window glass or a sunroof device that opens and closes a sunroof door at the top of the vehicle.
2. Related Art
A motor is used as a driving source for a power window device that opens and closes a vehicle door window glass up and down or a sunroof device that opens and closes a sunroof door. In the power window devices, a pinching restriction function is provided to restrict accidental pinching of passenger's body and foreign articles between a window glass and a window frame, for example. Among such power window devices equipped with the pinching restriction function, some devices have a limit switch provided at a specified position in the door and determine whether or not any obstacle has been pinched by the window glass based on a signal from the limit switch and a lock current of a motor to control movement of the window glass, that is, the rotation position of the motor. Other power window devices have a Hall IC or a special commutator for detecting the number of revolution of an armature to determine whether or not any obstacle has been pinched based on a revolution number detection signal (e.g., number or width of pulse signals) to control the rotation position of the motor.
However, in those power window devices having a motor rotation position detection mechanism, cumbersome adjustment of assembling position may be required when the motor and a window regulator are assembled, and cumbersome resetting after assembling work may also be required. Further, when the pinching restriction mechanism is provided, other additional expensive parts such as a control device may be required, but the accuracy is not improved so much.
In view of the foregoing problems, JP-A-8-29114 and JP-A-9-236431 disclose a position detector of a motor actuator for a moving body. The position detector for the moving body includes: a planetary gear train unit having a ring gear which is rotatably supported in a cover plate and planetary gears engaged with the ring gear; a switch portion having a moving contact plate which is formed integrally with the ring gear to rotate with the ring gear and a fixed contact terminal which is fixed on the cover plate to contact the moving contact plate; and a clutch mechanism which can shut off the transmission of the rotation force in the forward direction from the moving body (i.e., output shaft of motor) to the ring gear. Thus, when the position detector is applied to the power window device or the sunroof device, the position of the window glass or the sunroof door can be accurately detected to control the movement thereof. Further, the position detector can be readily set to the initial position without cumbersome positional adjustment, and these effects can be realized by a simple mechanism and in low cost.
Further, in the position detector, a pulse plate is integrally connected to a sun gear of the planetary gear train unit. As shown in FIG. 13, a pulse plate 300 is provided with a sequential pulse pattern. The pulse pattern has a ring-shaped first conductive unit 302 and a second conductive unit 304 disposed next to the first conductive unit 302, having a sequential pulse-shaped uneven surface. The pulse pattern is formed by plating metal material such as nickel on a resin plate. Further, a sliding contact 306 made of copper, for example, makes contact with the pulse plate 300. The sliding contact 306 is secured on the cover plate and has an input contact 306A which constantly makes contact with the first conductive unit 302 of the pulse plate 300 and an output contact 306B which makes contact with the second conductive unit 304 of the pulse plate 300.
When the pulse plate 300 rotates integrally with the sun gear, that is, with a moving body such as the motor output shaft, pulse signals are generated. Therefore, the generated pulse signals can be detected, and the moving position of the moving body can be linearly detected according to the detected signals. Thus, the position of the window glass can be constantly detected when the position detector is applied to the power window device.
However, in the above position detector for a moving body, grease tends to run out between the first conductive unit 302 of the pulse plate 300 and the input contact 306A of the sliding contact 306, because both the first conductive unit 302 and the input contact 306A are made of metal and constantly make contact (slide on) with each other. When this grease run-out occurs, the first conductive unit 302 and the input contact 306A may fuse at a high temperature, resulting in deterioration of position detection performance of the position detector.